Calls of the form data(package = pkg) inside a function
incorrectly fail ("pkg" is a local variable). For instance,
foo <- function(pkg) data(package = pkg)
foo("base")
Error in .find.package(package, lib.loc, verbose = verbose) :
none of the packages were found
## workaround -- force argument "package" to be an expression
## (not a name)
foo <- function(pkg) data(package = as.character(pkg))
all.equal(data(package = "base"), foo("base"))
[1] TRUE
The cause is the following piece of code inside data()
> print(data)
....
if (!missing(package))
if (is.name(y <- substitute(package)))
package <- as.character(y)
...
namely, when data() is invoked from within a function, e.g.,
data(package = pkg), the argument "package" inside data() is indeed
a name, but not one that should be coerced to character as when one
types data(base) from the R prompt, but rather simply a variable
in the calling function; in the example above, the arg "package"
to data() is effectively computed to be "pkg", which (luckily)
does not correspond to any attached package.
version
_
platform i686-pc-linux-gnu
arch i686
os linux-gnu
system i686, linux-gnu
status Patched
major 1
minor 8.0
year 2003
month 10
day 13
language R
--
David A. James
Statistics Research, Room 2C-253 Phone: (908) 582-3082
Bell Labs, Lucent Technologies Fax: (908) 582-3340
Murray Hill, NJ 09794-0636